This invention relates to a system and method for implanting a prosthesis, and more particularly, to a method for releasing a graft within a corporeal lumen.
It is well established that various fluid conducting body or corporeal lumens, such as veins and arteries, may deteriorate or suffer trauma so that repair is necessary. For example, various types of aneurysms or other deteriorative diseases may affect the ability of the lumen to conduct fluids. In some cases, the damaged lumen is repairable only with the use of prosthesis such as an artificial vessel or graft.
For repair of vital vessels such as the aorta, conventional surgery may be significantly life-threatening. Techniques known in the art which tend to minimize dangers to the patient include a procedure in which a graft resembling the natural vessel is placed within the diseased or obstructed section of the natural vessel.
More specifically, it is known within the art to provide a prosthesis for intraluminal repair of a vessel. In intraluminal vessel repair, the prosthesis is advanced, in a radially compressed configuration, intraluminally through the vessel to the repair site using a delivery catheter. After being properly positioned at the repair site, the prosthesis is deployed in its expanded state within the vessel so that the prosthesis traverses the diseased portion to thereby repair the vessel. The prosthesis is secured within the vessel with hooks or staples that are either self-expanding upon deployment or are mechanically extended utilizing balloon dilation.
Various methods of deployment of the graft once it is positioned at the repair site are known in the art. One method utilizes a sheath that holds the graft in a radially compressed configuration until it is removed therefrom. Another method utilizes a mechanical release system composed of a retractable wire or control cords to release the graft from its compressed configuration. A third method utilizes an electrolytic release system which employs a power-induced difference of potential to cause erosion of metal binding straps that hold a graft in a radially compressed state.
A drawback of the sheath method is the potential, in certain circumstances, for cocking or longitudinal movement of the graft caused when the sheath is retracted. A drawback of the mechanical release systems is the potential for entanglement or a stress-induced failure when the release wire or cords are retracted or when the graft is advanced within the vessel. A drawback of the electrolytic release system is that it can potentially take from 30 seconds to 5 minutes for the bindings retaining a graft to erode after application of the external voltage device.
Accordingly, there is a need for a device and associated method that avoids the potential shortcomings of conventional sheath systems and the potential failures of conventional mechanical systems, while enabling the graft to be released accurately and expeditiously within vasculature. The present invention fulfills these and other needs.
Briefly, and in general terms, the present invention provides a new and improved device and method for releasing a graft within vasculature. In one aspect, the invention employs a resistive wire element which, when heated, severs bindings retaining a graft in a radially compressed configuration. The present system can be configured to release the graft bindings simultaneously or in any desired order. The present system operates to release a graft in an expedient manner and can be incorporated for use in existing prosthesis implant systems which utilize a sheath, mechanical release, or electrolytic erosion mechanism with only minor modifications to the delivery catheter and graft material.
In another aspect of the invention, conducting wires are used to deliver current to a resistive wire element which is placed in a looped configuration. The conducting wires extend from external a patient""s body to a position adjacent the resistive wire. The resistive wire element can be made of material such as nichrome. The conducting wires can be made from standard circuitry wiring known in the art of medical electronics (i.e. copper with cladding). When heated by current supplied by an external voltage device, the resistive wire element severs the binding material which is threaded through the resistive wire loop. With the binding material cut, the graft is free to expand and secure itself to the vessel or be secured thereat by balloon dilation.
The graft can be tubular, bifurcated or modular. Preferably, the graft embodies woven polyester, or another material suitable for placement in the body such as PTFE, that allows the binding material to be threaded through the graft to engage the resistive wire loop.